(1) Field of the Invention
The present invention generally relates to a thermal recording apparatus used as, for example, a printer for facsimile machines, and more particularly to a thermal recording apparatus in which information can be recorded on and erased from a recording sheet formed of a thermal reversible material.
(2) Description of Related Art
In general, facsimile machines receive information automatically. Thus, unnecessary information transmitted as a direct mail can be received. In this case facsimile machine recording sheets are wasted unnecessarily. Since facsimile machines for home use frequently receive unnecessary information, a law prohibiting such facsimile transmission will be enacted in the U.S. Alternatively, a facsimile machine having a function for checking an ID code has been proposed in order to prevent the receipt of unnecessary information. However, a satisfactory result has not been obtained.
Existence of a recording sheet having a property that information recorded thereon can be erased therefrom would solve the above problem with regard to receiving unnecessary information. xe2x80x9cProceedings of 4th Japanese Symposium on Non-impact Printing Technologies Symposium; Thermal Reversible Material and Recording Characteristicsxe2x80x9d reports that a sheet formed of a thermal reversible material can be used as the above recording sheet having the property that recorded information can be erased therefrom. The thermal reversible material has a characteristic that it reversibly transits between a first state and a second state in accordance with a temperature thereof. The thermal reversible material may include a photochromic material and a thermochromic material, and can be made of an organic macromolecular substance.
The thermal reversible material reported by the above identified document can be maintained in either a first state referred to as a milky white state or a second state referred to as a transparent state. That is, the thermal reversible material transits reversibly between the milky white state and the transparent state in accordance with an amount of heat added thereto; each of the states can be maintained at the normal temperature. In the milky white state, the thermal reversible material is turbid milky white. In the transparent state, the thermal reversible material is transparent. The reversible transition between the milky white state and the transparent state is effected in accordance with variation of the size of each crystal in organic low molecular particles dispersed in the resin forming the thermal reversible material.
A thermal recording sheet made of thermal reversible material has a structure, for example, as shown in FIG. 1.
Referring to FIG. 1, the thermal recording sheet has a black base layer 1, a thermal reversible material layer 2 and a protection layer 3, which layers are stacked in this order. The black base layer 1 may be made, for example, of a plastic film, a metal plate or the like. The black base layer 1 may be also formed of a paper and an under coat layer coated on the paper. The protection layer 3 is transparent and made, for example, of silicon resin, silicon rubber, polyamide, polysiloxane graft polymer, or the like. The thermal reversible material layer 2 is made, for example, of the thermochromic material described above. The thermal reversible material layer 2 reversibly transits between the milky white state and the transparent state, as shown in FIG. 2. Referring to FIG. 2, the thermal reversible material layer 2 remains in the milky white state at the normal temperature Ta. The thermal recording sheet is heated by a thermal head so that the temperature of the thermal reversible material layer 2 reaches a first temperature Tb. As a result, the thermal reversible material layer 2 transits from the milky white state to the transparent state, as shown by a solid line in FIG. 2. After this, the temperature of the thermal reversible material layer 2 decreases to the normal temperature Ta. At the normal temperature Ta, the thermal reversible material layer 2 is maintained in the transparent state. In a case where the thermal reversible material layer 2 is in the transparent state, the black base layer 1 is visible through the thermal reversible material layer 2 and the protection layer 3. Thus, due to heating the milky white recording sheet in a dotted pattern from the normal temperature Ta to the first temperature Tb, a black image corresponding to the dotted pattern is formed on the milky white recording sheet, as shown in FIG. 3.
When the thermal reversible material layer 2 is in the transparent state, the thermal recording sheet is heated by the thermal head so that the temperature of the thermal reversible material layer 2 reaches a second temperature Tc. As a result, the transmittance of the thermal reversible material layer 2 decreases, as shown by a dashed line in FIG. 2. Then the temperature of the thermal reversible material layer 2 decreases and reaches the normal temperature Ta, so that the thermal reversible material layer 2 returns to the milky white state. The thermal reversible material layer 2 remains in the milky white state at the normal temperature Ta. When the thermal reversible material layer 2 is in the milky white state, the thermal recording sheet is milky white. Thus, due to heating the thermal recording sheet on which the black image appears, to the second temperature Tc, the black image is erased from the milky white recording sheet.
An image forming apparatus using the thermal recording sheet made of thermal reversible material has been proposed in U.S. Pat. Nos. 4,839,731 and 4,851,924. In the conventional image forming apparatus disclosed in the references, a heating device (a thermal head) for recording images on the thermal recording sheet and a heating device for erasing the images therefrom are separated from each other. Since two separate thermal devices are required for recording and erasing images on and from the thermal recording sheet, a cost of the conventional image forming apparatus is high.
Accordingly, a general object of the present invention is to provide a novel and useful thermal recording apparatus using a recording sheet made of a thermal reversible material in which the disadvantages of the aforementioned prior art are eliminated.
A more specific object of the present invention is to provide a thermal recording apparatus in which information recorded on a recording sheet made of a thermal reversible material can be erased therefrom without increasing cost of the thermal recording apparatus.
The above objects of the present invention are achieved by a thermal recording apparatus for recording information on a thermal recording medium, the thermal recording medium having a thermal characteristic by which the information is recorded thereon by heating the thermal recording medium at a first temperature and information that has been recorded on the thermal recording medium is erased therefrom by heating the thermal recording medium to a second temperature, the thermal recording apparatus comprising: a thermal head for heating the thermal recording medium in a pattern; recording means, coupled to the thermal recording medium and the thermal head, for driving the thermal head so that the thermal recording medium is heated to the first temperature in a pattern corresponding to the information to be recorded; and erasing means, coupled to the thermal recording medium and the thermal head, for supplying thermal energy to the thermal recording medium on which information has been recorded by using the thermal head so that the thermal recording medium is heated to the second temperature, wherein when recording, the recording means is activated in order to form the information on the thermal recording medium, and when erasing, the erasing means is activated in order to erase the information from the thermal recording medium.
The above objects are also achieved by a thermal recording apparatus for recording information on a thermal recording medium, the thermal recording medium having a thermal characteristic by which the information is recorded thereon through heating the thermal recording medium to a first temperature and the information recorded on the thermal recording medium is erased therefrom through heating the thermal recording medium to a second temperature, the thermal recording apparatus comprising: a thermal head for heating the thermal recording medium in a pattern; recording means, coupled to the thermal recording medium and the thermal head, for driving the thermal head so that the thermal recording medium is heated to the first temperature in a pattern corresponding to the information to be recorded; reading means for reading the thermal recording medium on which information has been recorded; setting means, coupled to the reading means, for setting an erasing area on the thermal recording medium based on a result obtained by the reading means, the erasing area including a pattern corresponding to the information recorded on the thermal recording medium; and erasing means, coupled to the thermal recording medium, the thermal head and the setting means, for supplying thermal energy to the erasing area set on the thermal recording medium by using the thermal head so that the erasing area on the thermal recording medium is heated to the second temperature, wherein the recording means is activated in order to form the information on the thermal recording medium, and the reading means, the setting means and the erasing means are activated in order to erase previously recorded information from the thermal recording medium.
According to the present invention, recording of information on the thermal recording medium and erasing of recorded information therefrom can be performed by using a single thermal head.
Additional objects, features and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.